A tandem-type color laser printer disclosed in Japanese Patent-Application Publication No. 2006-96527 includes a belt unit for conveying a recording sheet and a photosensitive unit having photosensitive drums. Since it is necessary to perform maintenance operations to fix paper jam occurred during an image forming operation in a paper conveying path or to replenish consumables, such as developer, the belt unit and the photosensitive unit are configured to be detachable from a main body of the laser printer.
In case of a configuration in which a regular mounting position of the photosensitive unit in the main body is in a path through which the belt unit is mounted to or removed from the main body, it is necessary to mount the belt unit to the main body before mounting the photosensitive unit to the main body.
With this configuration, when the photosensitive unit is inserted to the main body while the belt unit is improperly and incompletely mounted to the main body, the photosensitive unit collides with part of the belt unit, and the photosensitive unit cannot be mounted to the main body. Also, parts of the belt unit and the photosensitive unit that collide with each other may be damaged.
In order to solve this problem, it is conceivable to promote awareness about the necessity of confirming whether the belt unit has been mounted to a proper mounting position before inserting the photosensitive unit into the main body. However, this method cannot fundamentally solve the problem.